Gallium nitride-based compound semiconductor materials have become of major interest recently as a semiconductor material for a short-wavelength light emitting device. A gallium nitride-based compound semiconductor is formed on various substrates made of oxides, principally a sapphire single crystal, and III-V group compounds using a metal-organic chemical vapor deposition method (MOCVD method) or a molecular beam epitaxy method (MBE method).
In a gallium nitride-based compound semiconductor light emitting device, light from a light-emitting layer is efficiently emitted to the outside using, as a positive electrode, a transparent electrode such as an ITO electrode and an AuNi transparent electrode. In order to improve light emission efficiency, various LED chips have been proposed with a design arranging electrodes such as a pad electrode on a transparent electrode and a negative electrode on an n-type layer (for example, refer to Japanese Unexamined Patent Publication (Kokai) No. 2005-19646).
The modularization of LED chips results in a higher need for replacement of a conventional square shape with a rectangular shape, especially a modified shape, so as to make efficient use of space, for the following reason. In a chip where light is irradiated in a lateral direction, a square shape is inefficient with respect to mounting, and therefore a rectangular shape capable of decreasing the height of a module is desired. However, in an LED chip having a rectangular shape, a distance between electrodes and an electrode shape results in a problem such as a deterioration in the high light extraction efficiency which could be achieved in the prior art. For example, in Japanese Unexamined Patent Publication (Kokai) No. 2004-221529, an opaque electrode for diffusion is formed on a transparent electrode which is originally formed so as to extract light, thus sacrificing an emission output of the entire light emitting device.